We have compared the performance of our in-house constructed delayed-extraction linear MALDI-TOF instrument with our newly acquired commercial PerSeptive STR MALDI-TOF instrument with respect to sensitivity and mass spectrum quality. In linear mode, our in-house constructed instrument appears to be approximately one order of magnitude more sensitive than the commercial instrument (I finale amounts of peptide give signals with signal-to-noise ratios in excess of 100: 1 in the in-house constructed device). The commercial instrument gives very high quality spectra for -10fmol amounts of peptide in the reflecting mode. We continue to implement improvements to the commercial instrumentation that we believe will ultimately lead to further enhancements in performance.